Prosthetic apparatuses are widely used in medical procedures to restore appearance and/or function of lost or damaged body parts, such as joints, hips, bones, and teeth. One problem associated with prosthetic apparatuses is the colonization of harmful bacteria on the surface of the prosthetic apparatuses, especially between closely fitted components. Such colonization of harmful bacteria may affect proper function of the prosthetic apparatus and may cause infection or other adverse effects to surrounding tissues, requiring removal and replacement of the prosthetic apparatus and timely treatment of the infective or otherwise adverse conditions.
For example, while using dental implants to improve oral function is state-of-the-art, and has proven effective and reliable over the years, crestal bone loss remains a common problem associated with the prosthetic treatment and, over time, may jeopardize the effectiveness the prostheses if it leads to implant mobility and failure. While the exact reason for the crestal bone loss is unknown, it may be caused by biological and/or mechanical conditions surrounding the crestal bone tissue.
Current dental prostheses generally include three components to fully define the artificial tooth root: an implant component, which is placed into the prepared osteotomy; an abutment component, which is an extensory unit installed into the implant; and a fixation screw to interconnect the implant and abutment components. The mating fits among the components are predetermined by design and tolerance, and often leave small gaps, or “microgaps”, among mated components despite efforts by manufacturers to reduce such microgaps. The microgap may vary in dimension depending on design (e.g. cement-retained or screw-retained) and loading condition of the dental prostheses. For example, the microgap may be from 5-10 micrometer and sometime can be as wide as more than 60 micrometers.
Studies have shown that known pathogenic bacteria can attach onto the components of dental prostheses. Upon attachment, the sharp edges and undercuts of the microgap create a shelter for pathogenic bacteria to colonize within the microgap and eventually spread to tissues surrounding the dental prostheses. Further, mechanical stress on the components of the dental prostheses may lead to “pumping” of the pathogenic bacteria out of the microgap to facilitate the spread of the pathogenic bacteria.
Efforts to manage pathogenic colonization of the microgap have been met with limited success. Regular dental hygiene has been proven ineffective, as the microgap is smaller than most brush tips and is often submerged in soft or sensitive tissue. Systemic prophylactics have limited effects in the oral environment, as bacteria tends to rapidly aggregate into protected clusters, reducing the efficacy of traditional medicine and increasing the chance of generating antibiotic-resistant bacteria.
Current attempts to address this problem focus on site specific methods to control bacterial colonization within the microgap. For example, some methods attempt to reduce the microgap through tighter component fits and reduced tolerances. Other methods use prosthetic components that medialize the microgap, creating distance between the microgap and crestal bone. Finally, the dental prosthesis may be designed as a single piece or single stage implant or to have the microgap completely filled with cement. However, those are mechanical solutions that try to address the severity or frequency of the symptoms, not the underlying biological cause.
On the other hand, efforts have been directed toward preventing bacterial colonization in medical devices by the use of antimicrobial agents, such as antibiotics. Various methods have previously been employed to contact or coat the surfaces of medical devices with an antimicrobial agent. For example, one method involves flushing the surfaces of the device with an antimicrobial containing solution. Generally, the flushing technique would require convenient access to the site of bacterial colonization, which may be difficult if the site is blocked by body tissues, such as gums. Moreover, the use of antibiotics may trigger bacterial mutation and lead to antibiotic-resistant bacteria. Finally, bacterial colonization may lead to formation of a protective biofilm (e.g. glycocalyx) around the pathogenic bacteria, which may further limit the access and effectiveness of antibiotics.
Alternatives to traditional antibiotics include the use of chemical coatings to create a bactericidal environment. Copper (Cu) and Silver (Ag) are undergoing investigation as non-selective methods for bacterial resistance. However, these methods can produce free radicals, damaging redox reactions in surrounding tissue, and reduce in effectiveness as the body begins coating the affected surface with proteins.
Probiotic microorganisms are also known in general medical hygiene. For example, compositions containing probiotic microorganisms may be used on human skin or oral cavity to inhibit contamination of pathogenic bacteria. Moreover, probiotic microorganisms may be applied through a spray or cleaning wipe to surfaces such as tables, benches, hospital fixtures, equipment, clothing, and beddings. However, use of probiotic microorganisms in prosthetic apparatuses, especially where biological and mechanical conditions are different from known applications, has not been attempted or suggested.